For “wall mounted” thermostats meant for homes and offices. Ones with enough technical capability to run EOPs appear to mostly be Linux/ARM devices, but some run Windows embedded.

All software versions of the Nest Thermostat are affected by this root package

A lot of hacks are available for this, and some of them allow root and SSH access. Things can be rendered to the display, but further functionality is unknown.

https://www.exploitee.rs/index.php/Nest_Hacking

https://www.youtube.com/watch?v=H3tmvpi4YR0

https://www.exploitee.rs/index.php/Exploiting_Nest_Thermostats

The system boots from spi flash so it's easy to backup or replace it.

The given port is quite fully featured, capable of basic web server hosting, picture displaying, internet browsing, and much more. No code is supplied, but instructions are available to replicate. While the Doom port is included for notoriety, it does not utilize any OS, thus keeping it within this.

https://hackaday.com/2019/06/10/running-linux-on-a-thermostat/

https://www.youtube.com/watch?v=iQKnL692q0w

https://hackaday.com/2017/05/22/doomed-thermostat/

https://www.youtube.com/watch?v=2T5LyEjLfP8

This is what runs stock on this thing, and apparently at times it will display parts of the original Windows shell. Quite cool.

https://www.reddit.com/r/Windows10/comments/fuv3g8/hey_i_recognize_this_screen_from_anywhere_this_is/